366 PRACTICE OF PHYSIC. 



of syncope, it may be observed, that, as the exertions of the 

 energy of the brain are especially under the influence of the 

 will, so it is well known that those modifications of the will 

 which are named Passions and Emotions, have a powerful in- 

 fluence on the energy of the brain in its actions upon the heart, 

 either in increasing or diminishing the force of that energy. 

 Thus, anger has the former, and fear the latter effect ; and 

 thence it may be understood how terror often occasions a syn- 

 cope sometimes of the most violent kind, named Asphyxia, and 

 sometimes death itself. 



MCLXXXI. As, from what I have just mentioned, it ap- 

 pears that the emotions of desire increase, and those of aversion 

 diminish the energy of the brain ; so it may be understood haw 

 a strong aversion, a horror, or the feeling which arises upon the 

 sight of a very disagreeable object, may occasion fainting. As 

 an example of this, I have known more than one instance of a 

 person's fainting at the sight of a sore in another person. 



MCLXXXII. To this head of horror and disgust, I refer 

 the operation of those odours which in certain persons occasion 

 syncope. It may be supposed, that those odours are endowed 

 with a directly sedative power, and may thereby occasion syn- 

 cope ; but they are, many of them, with respect to other per- 

 sons, evidently of a contrary quality : and it appears to me, that 

 those odours occasion syncope only in those persons to whom 

 they are extremely disagreeable. 



MCLXXXIII. It is, however, very probable that, among 

 the causes of syncope, there are some which, analogous to all 

 those we have already mentioned, act by a directly sedative 

 power ; and such may either be diffused in the mass of blood, 

 and thereby communicated to the brain, or may be only taken 

 into the stomach, which so readily and frequently communicates 

 its affections to the brain. 



MCLXXXIV. Having now enumerated, and, as I hope, 

 explained the most part of the remote causes of syncope, that 

 either operate immediately upon the brain, or whose operation 

 upon other parts of the body is communicated to the brain, it is 

 proper to observe, that the most part of these causes operate 

 upon certain persons more readily and more powerfully than 

 upon others ; and this circumstance, which may be considered 

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